The overall goal of Project 3 is to understand how p66Shc knockout (KO) and diet controls the regenerative and differentiation potentials of stem cells, and the consequences of this regulation in determination of resistance to cell stress and adiposity. This project has two specific aims: Aim 1 is to further characterize the effects of the p66Shc genotype on regenerative and differentiation potentials on stem cells of multiple compartments, e.g., epithelial, hematopoietic, mesenchymal, adipose, and muscle, already defined in substantial preliminary data of the Pelicci and Rizzuto groups. The goal is to clarify the signals and the molecular checkpoints pf the proliferative and differentiation routes, and the alterations induced by patho-physiological alterations, such as obesity and hyperglycemia, as well as to determine the cellular identity of the precursor cells responsible for regeneration, and the signals and transduction mechanisms of trans-differentiation into other cell lineages. Finally, Project 3 will determine how diet, i.e., lifespan-lengthening calone restriction, low-carbohydrate diet and high-fat diet, influence stem cell proliferation and differentiation. Aim 2 will determine the mechanism of ShcKO muscle stress resistance, investigating increased regenerative/differentiation potential of stem cells and activation of autophagy pathway. The Rizzuto group has already identified enhanced stress-induced autophagy in p66Shc -/- muscles. The project's research program will determine the basis of increased stress resistance of p66Shc muscle, which could include increased regenerative capacity, decreased differentiation to adipose, and increased autophagy. To achieve this, project personnel will investigate the signaling pathways, with major emphasis on the Akt/FoxO/Bnip pathway and on signals converging on mitochondna (assembly of regulatory complexes on the mitochondnal membrane, organelle morphology, calcium transients). Then the project will investigate these effects in the context of calorie-restriction and low-carbohydrate diets.